Allow throws / throwsAsync to work with any value, not just errors

[novemberborn]

t.throws() and t.throwsAsync() require the resulting exception to be a proper error:

ava/lib/assert.js

Lines 147 to 154 in 952a017

	if (!isError(actual)) {
	throw new AssertionError({
	assertion,
	message,
	savedError,
	values: [formatWithLabel(`${prefix} exception that is not an error:`, actual)]
	});
	}

I propose we add an any: boolean option to the expectations object used for these assertions. If true it won't cause a failed assertion when the exception is not an error.

We need to update the validation logic here to allow this property:

ava/lib/assert.js

Line 74 in 952a017

function validateExpectations(assertion, expectations, numberArgs) { // eslint-disable-line complexity

Don't forget to update the type definition:

ava/index.d.ts

Line 11 in 952a017

export type ThrowsExpectation = {

If any is true, we should try and change the typing of the return value to be unknown:

ava/index.d.ts

Line 252 in 952a017

<ThrownError extends Error>(fn: () => any, expectations?: ThrowsExpectation | null, message?: string): ThrownError;

ava/index.d.ts

Line 263 in 952a017

<ThrownError extends Error>(fn: () => PromiseLike<any>, expectations?: null, message?: string): Promise<ThrownError>;

And update our own tests:

ava/test-tap/assert.js

Line 786 in 952a017

test('.throws()', gather(t => {

ava/test-tap/assert.js

Line 976 in 952a017

test('.throwsAsync()', gather(t => {

See also the discussion in #1841.

[sindresorhus]

I think we should add a short note to the docs that if the user is in control of the error, they should prefer to make it a proper Error.

[randomicon00]

Hello @novemberborn & @sindresorhus, I would like to tackle this issue if possible.

Thank you,

[novemberborn]

@randomicon00 that's great go for it 😄

[randomicon00]

@novemberborn Will do thanks :)

[adiSuper94]

@novemberborn I'd like to take a crack at this.

[randomicon00]

It assigned to me, I still didn't complete it but you can try I guess. I am still working on it.

[adiSuper94]

@randomicon00 , it's cool if you are working on it. I though that it was inactive, so asked.

[adiSuper94]

@novemberborn I'd still like to take a crack at this.

[novemberborn]

By all means @adiSuper94! I'm low on time but I do want this in for AVA 6. Hopefully you get to it before I do 😀

[adiSuper94]

I have added a PR that tries to fix this.
@novemberborn your comments outlining the places for code change was very helpful. Thank you.

If any is true, we should try and change the typing of the return value to be unknown

I am a bit confused about this. The signature of the throws/throwsAsync function itself doesn't seem change.
The return type of of the function passed to throws/throwsAsync is any.
And even if it throws a non error value, wouldn't the return type still remain the same?

If I am missing anything could you explain how this can be done ?